894 research outputs found
Scaling up qualitative data: with Professor Ken Benoit
No full textProfessor Benoit is the Principal Investigator in an ERC funded project QUANTESS developing innovative methods for the quantitative analysis of textual data in the social sciences. He is the co-author with Paul Nulty of the R software package for text analysis “quanteda”, and working on a book Quantitative Text Analysis Using R covering methods for managing, processing, and analysing textual data using the R programming language. He has taught quantitative text analysis extensively and has published research in this area targeting both methodology and political science applications
Thesium philosophicarum fasciculus
No full textquem ... praeside ... Io. Friderico Benoit ... publicè tutabitur Ioh. Rodolphus Kochius, HBernas, phil. stud. author & respondens, ad diem 5. Martii ...Diss. Hohe Schule Bern, 171
New Evidence on the Determinants of Absenteeism Using Linked Employer-Employee Data
No full textIn this paper, we provide new evidence on the determinants of absenteeism using the Workplace Employee Survey (WES) 1999-2002 from Statistics Canada. Our paper extends the typical labour-leisure model used to analyze the decision to skip work to include firm-level policy variables relevant to the absenteeism decision and uncerainty about the cost of absenteeism. It also provides a non-linear econometric model that explicitly takes into account the count nature of absenteeism data and unobserved heterogeneity at both the individual and firm level. Controlling for very detailed demographic, job and firm characteristics (including workplace practices), we find that dissatisfaction with contracted hours is a significant determinant of absence.Absenteeism, Linked Employer-Employee Data, Unobserved Heterogeneity, Count Data Models
New Evidence on the Determinants of Absenteeism Using Linked Employer-Employee Data
No full textIn this paper, we provide new evidence on the determinants of absenteeism using the Workplace Employee Survey (WES) 1999-2002 from Statistics Canada. Our paper extends the typical labour-leisure model used to analyze the decision to skip work to include firm-level policy variables relevant to the absenteeism decision and uncertainty about the cost of absenteeism. It also provides a non-linear econometric model that explicitly takes into account the count nature of absenteeism data and unobserved heterogeneity at both the individual and firm level. Controlling for very detailed demographic, job and firm characteristics (including workplace practices), we find that dissatisfaction with contracted hours is a significant determinant of absence.Absenteeism; Linked Employer-Employee Data; Unobserved Heterogeneity; Count Data Models.
Analyse numérique des bifurcations dans les systèmes d'équations différentielles paramétrées.
No full textCette thèse porte sur l'étude numérique de systèmes d'équations différentielles paramétrées de la forme u&d2; =fu,a, 1 ou u ∈ R n, a ∈ R m, n, m < infinity et f : R n x R m → R n est suffisamment continûment différentiable. Nous montrons comment calculer numériquement des branches de solutions stationnaires de (1) à partir d'un point d'équilibre. Puis, nous indiquons comment identifier certains types de bifurcations, ce qui permet de dresser un diagramme de bifurcation partiel de (1). Nous utilisons ensuite la présence de symétrie pour simplifier l'étude numérique de (1). Finalement, nous présentons une série d'exemples qui illustrent l'utilisation des algorithmes et des concepts étudiés
Analyse numérique des bifurcations dans les systèmes d'équations différentielles paramétrées.
No full textCette thèse porte sur l'étude numérique de systèmes d'équations différentielles paramétrées de la forme u&d2; =fu,a, 1 ou u ∈ R n, a ∈ R m, n, m < infinity et f : R n x R m → R n est suffisamment continûment différentiable. Nous montrons comment calculer numériquement des branches de solutions stationnaires de (1) à partir d'un point d'équilibre. Puis, nous indiquons comment identifier certains types de bifurcations, ce qui permet de dresser un diagramme de bifurcation partiel de (1). Nous utilisons ensuite la présence de symétrie pour simplifier l'étude numérique de (1). Finalement, nous présentons une série d'exemples qui illustrent l'utilisation des algorithmes et des concepts étudiés
Applications of Filippov's Method to Modelling Avian Influenza
No full textAvian influenza is a contagious viral disease caused by influenza\ud
virus type A. Avian influenza can be disastrous (if it occurs), due to\ud
the short incubation period (about 1--4 days). Thus it is important to\ud
study this disease so that we are more prepared to manage it in the\ud
future. A classical system of differential equations (the\ud
half-saturated incidence model) and three Filippov models --- an\ud
avian-only model with culling of infected birds, an SIIR\ud
(Susceptible-Infected-Infected-Recovered) model with quarantine of\ud
infected humans and an avian-only model with culling both susceptible\ud
and infected birds --- that are governed by ordinary differential\ud
equations with discontinuous right-hand sides (i.e., differential\ud
inclusion) are proposed to study the transmission of avian\ud
influenza. The effect of half-saturated incidence is investigated, and\ud
the outcome of this model is compared with the bilinear incidence\ud
model. Both models remain endemic whenever their respective basic\ud
reproduction numbers are greater than one. The\ud
half-saturated incidence model generates more infected individuals\ud
than the bilinear incidence model. This may be because the\ud
bilinear incidence model is underestimating the number of infected\ud
individuals at the outbreak. For the Filippov models,\ud
the number of infected individuals is used as a reference in applying\ud
control strategies. If this number is greater than a threshold value,\ud
a control measure has to be employed immediately to avoid a more\ud
severe outbreak. Otherwise, no action is necessary. We perform\ud
dynamical system analysis for all models. The existence of sliding\ud
modes and the flow on the discontinuity surfaces are determined. In\ud
addition, numerical simulations are conducted to illustrate the\ud
dynamics of the models. Our results suggest that if appropriate\ud
tolerance thresholds are chosen such that all trajectories of the\ud
Filippov models are converging to an equilibrium point that lies in\ud
the region below the infected tolerance threshold or on the\ud
discontinuity surface, then no control strategy is necessary as we\ud
consider the outbreak is tolerable. Otherwise, we have to apply\ud
control strategies to contain the outbreak. Hence a well-defined\ud
threshold policy is crucial for us to combat avian influenza\ud
effectively
Steady State/Hopf Interactions in the Van Der Pol Oscillator with Delayed Feedback
No full textIn this thesis we consider the traditional Van der Pol Oscillator with a forcing dependent on a delay in feedback. The delay is taken to be a nonlinear function of both position and velocity which gives rise to many different types of bifurcations. In particular, we study the Zero-Hopf bifurcation that takes place at certain parameter values using methods of centre manifold reduction of DDEs and normal form theory. We present numerical simulations that have been accurately predicted by the phase portraits in the Zero-Hopf bifurcation to confirm our numerical results and provide a physical understanding of the oscillator with the delay in feedback
Steady State/Hopf Interactions in the Van Der Pol Oscillator with Delayed Feedback
No full textIn this thesis we consider the traditional Van der Pol Oscillator with a forcing dependent on a delay in feedback. The delay is taken to be a nonlinear function of both position and velocity which gives rise to many different types of bifurcations. In particular, we study the Zero-Hopf bifurcation that takes place at certain parameter values using methods of centre manifold reduction of DDEs and normal form theory. We present numerical simulations that have been accurately predicted by the phase portraits in the Zero-Hopf bifurcation to confirm our numerical results and provide a physical understanding of the oscillator with the delay in feedback
Applications of Filippov's Method to Modelling Avian Influenza
No full textAvian influenza is a contagious viral disease caused by influenza
virus type A. Avian influenza can be disastrous (if it occurs), due to
the short incubation period (about 1--4 days). Thus it is important to
study this disease so that we are more prepared to manage it in the
future. A classical system of differential equations (the
half-saturated incidence model) and three Filippov models --- an
avian-only model with culling of infected birds, an SIIR
(Susceptible-Infected-Infected-Recovered) model with quarantine of
infected humans and an avian-only model with culling both susceptible
and infected birds --- that are governed by ordinary differential
equations with discontinuous right-hand sides (i.e., differential
inclusion) are proposed to study the transmission of avian
influenza. The effect of half-saturated incidence is investigated, and
the outcome of this model is compared with the bilinear incidence
model. Both models remain endemic whenever their respective basic
reproduction numbers are greater than one. The
half-saturated incidence model generates more infected individuals
than the bilinear incidence model. This may be because the
bilinear incidence model is underestimating the number of infected
individuals at the outbreak. For the Filippov models,
the number of infected individuals is used as a reference in applying
control strategies. If this number is greater than a threshold value,
a control measure has to be employed immediately to avoid a more
severe outbreak. Otherwise, no action is necessary. We perform
dynamical system analysis for all models. The existence of sliding
modes and the flow on the discontinuity surfaces are determined. In
addition, numerical simulations are conducted to illustrate the
dynamics of the models. Our results suggest that if appropriate
tolerance thresholds are chosen such that all trajectories of the
Filippov models are converging to an equilibrium point that lies in
the region below the infected tolerance threshold or on the
discontinuity surface, then no control strategy is necessary as we
consider the outbreak is tolerable. Otherwise, we have to apply
control strategies to contain the outbreak. Hence a well-defined
threshold policy is crucial for us to combat avian influenza
effectively
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